Study of the aromatic by-products formed from ozonation of anilines in aqueous solution

Aqueous solutions of aniline and p-chloroaniline were treated with ozone in order to study the reaction and oxidation by-products. Aniline solutions were ozonated at low and high pH, so as to compare both molecular and hydroxyl free radical mechanisms, respectively. The main identified aromatic by-products were nitrobenzene and azobenzene when the experiment was carried out at acid pH. Formation of nitrobenzene, azobenzene, azoxybenzene and 2-pyridine-carboxylic was observed when the ozonation was carried out at basic pH. p-Chloroaniline was treated with ozone only at high pH and the identified by-products were in accordance with those obtained in the ozonation of aniline: p-chloronitrobenzene, 4,4'-dichloroazobenzene and 4-chloro-2-pyridine-carboxylic acid. All the aromatic by-products found were less toxic than the raw materials. The pseudo-first-order constants in aniline concentration were calculated, whilst kinetic in p-chloroaniline concentration could not be adjusted to a first-order reaction.     

Optical properties of the synthetic nanocomposites SiO2/CdS/poly(styrene-co-maleic anhydride) and SiO2/CdS/poly(styrene-co-maleimide)

Hybrid materials consisting of SiO2/CdS particles dispersed in poly(styrene-co-maleic anhydride) and poly(styrene-co-maleimide) have been synthesized and characterized. The polymer nanocomposites were synthesised in situ in the presence of previously prepared inorganic fillers (SiO2/CdS). The nanocomposites were synthesized with the use of as-prepared or surface-modified SiO2/CdS fillers. For both types of nanocomposites, the optical properties were evaluated and the observation of size quantization effects in the optical spectra is discussed. In this context, the influence of the inorganic fillers and polymer matrices on the optical properties of the final nanocomposites was investigated.     

Detection and resolution of intermediate species in protein folding processes using fluorescence and circular dichroism spectroscopies and multivariate curve resolution

Thermally induced protein unfolding/folding processes have been studied on alpha-lactalbumin and alpha-apolactalbumin. Experiments monitored by fluorescence and circular dichroism spectroscopic techniques on alpha-apolactalbumin showed the formation of an intermediate species, whereas in the case of alpha-lactalbumin, this intermediate species was not detected. The presence and resolution of this intermediate species, its spectrum, and the evolution of all conformations during protein unfolding/folding processes were estimated using the multivariate curve resolution-alternating least-squares method. Elucidation of the nature and contribution of the different secondary structure motifs in each of the resolved protein conformations, including the intermediate, was also carried out. Multivariate resolution has shown to be an excellent tool for the complete characterization of all protein conformations involved in folding processes, including intermediate species that cannot be isolated by physical or chemical means. Indeed, it is in the determination and modeling of these intermediates that this chemometric approach outperforms in power and reliability previous methodologies based on simpler measurements and data treatments and fills the void linked to the elucidation and interpretation of complex mechanisms in protein folding processes.     

Testing the robustness of the job demands-resources model.

[Correction Notice: An erratum for this article was reported in Vol 14(2) of International Journal of Stress Management (see record 2007-07240-008). Several corrections of errata in a paper by the authors published in the 2006 issue of the International Journal of Stress Management are presented: (1) The sentence beginning on page 385, line 16 should read "To avoid identification problems, the error variance of Organizational commitment and Emotional load were constrained using the formula (1 - α) × sigma2." (2) The sentence on page 385, line 18, should be deleted. (3) Degrees of freedom for M3 in Table 2 were incorrectly reported. The correct degrees of freedom were 54. The corrected table is provided.] According to the job demands-resources (JD-R) model, job demands and resources evoke two relatively independent processes: health impairment and employee motivation. The robustness of the JD-R model was tested in two different occupational samples, the first of 654 Spanish employees and the second of 477 Dutch employees. Structural equation modeling analyses provided partial evidence for the two processes. Multigroup analyses showed that the structural paths of the model were invariant across countries, although the strength of the relationships differed. We conclude that the basic structure of the JD-R model is maintained, even when applied in different national and occupational contexts, when using different ways of gathering data (computerized versus paper and pencil), and when using slightly different measures to assess the key variables of the model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of yttrium on the performances of zirconia based catalysts for the decomposition of N2O at high temperature

Abatement processes for the reduction of N₂O emissions from acid nitric plants can be implemented in different positions. Among the different possibilities, a catalytic process set up between the ammonia converter and the absorber could be a practicable solution. In those running conditions, at high temperature, in the presence of NO, O₂ and water, the catalytic decomposition of N₂O (in the absence of a reducing agent) can take place. However, catalysts usually suffer from a strong deactivation owing to the occurrence of thermal sintering which significantly lowers their specific surface area. Catalytic testing performed at laboratory scale showed that zirconia based catalysts stabilised by yttrium incorporation could be of potential interest. However, the mode of yttrium incorporation seems to be a key factor. According to the preparation procedure, surface yttrium enrichment may occur and then strongly inhibit the catalytic decomposition of N₂O. Co-precipitation methods can be profitably used for the preparation of modified-ZrO₂ catalysts in order to obtain yttrium homogeneously distributed in the bulk material. According to this preparation method, a synergy effect on the catalytic activity and also on the stability has been observed on ZrO₂ containing low amount of yttrium whereas an inhibiting effect prevails on highly loaded yttrium based catalysts irrespective of the mode of yttrium incorporation.     

A regression model describing the effect of pH,NaCl and temperature on<Emphasis Type="Italic"> D</Emphasis> values of<Emphasis Type="Italic"> Bacillus stearothermophilus</Emphasis> spores

A new microbiological predictive model was developed, relating pH, NaCl concentration and temperature (T) with the decimal reduction coefficient D as dependent variable, using data previously reported by [1]. The model was obtained by multiple linear regression using only three predictor variables (T ², pH² and NaCl), easily computed from the basic variables pH, NaCl concentration and temperature (T). The fitted model is robust, stable and satisfies all the basic hypotheses of the regression models. It also provides simplicity when compared with previously published models based on multiple linear regression tools.     

Hybrid ceramic-polymer material for wood coating with high wearing resistance

The synthesis and characterization of a hybrid ceramic-polymer coating with high wearing resistance and designed to cover wood surfaces, are reported in this work. This hybrid material provides a high wearing resistance (400% higher than a conventional commercial product typically used to protect these surfaces); additionally it has a high UV resistance and high transparency and gloss. The wood surfaces were previously treated either with a primer coating or with a special coupling agent, before the hybrid coating was applied; in both cases, good adhesion with the substrate was obtained. Electronic Publication     

Nanohybrid scratch resistant coatings for teeth and bone viscoelasticity manifested in tribology

We cover teeth surfaces with nanohybrid coatings containing an inorganic ceramic and an organic copolymer constituents. We report the first ever values of scratch penetration depth and scratch recovery for bare and coated teeth. We find that uncoated teeth undergo viscoelastic recovery (healing) after microscratching – the first manifestation of bone viscoelasticity in tribology. The coatings fill "valleys" in teeth surfaces. In each case a large improvement in the scratch resistance as compared to uncoated teeth is seen. The extent of the improvement depends on the inorganic/organic component ratios in the nanohybrids. Electronic Publication     

Skew product cycles with rich dynamics: From totally non-hyperbolic dynamics to fully prevalent hyperbolicity

We introduce a two-parameter family of ‘partially hyperbolic’ skew products (G_{a, t})_{a > 0, t ∈ [ ? ε, ε]} maps with one dimensional centre direction. In this family, the parameter a models the central dynamics and the parameter t the unfolding of cycles (that occurs for t = 0). The parameter a also measures the ‘central distortion’ of the systems: for small a, the distortion of the systems is small and it increases and goes to infinity as a → ∞. The family (G_{a, t}) displays some of the main characteristic properties of the unfolding of heterodimensional cycles as intermingled homoclinic classes of different indices and secondary bifurcations via collision of hyperbolic homoclinic classes. For a ∈ (0, log?2), the dynamics of (G_{a, t}) is always non-hyperbolic after the unfolding of the cycle. However, for a > log?4 intervals of t-parameters corresponding to hyperbolic dynamics appear and turn into totally prevalent as a → ∞ (the density of ‘hyperbolic parameters’ goes to 1 as a → ∞). The dynamics of the maps G_{a, t} is described using a family of iterated function systems modelling the dynamics in the one-dimensional central direction.